Rodenticidal and rodent repellent compositions

ABSTRACT

Rodent repellent and rodenticidal compositions containing as the active ingredient 1-(2-imidazolin-2-ylmethyl)-3-ethylindole and methods of combatting rodents comprising orally administering an effective rodent repellent or rodenticidal quantity of the active ingredient.

[ 1 Sept. 5, 1972 [54] RODENTICIDAL AND RODENT REPELLENT COMPOSITIONS[72] Inventors: Franklin J. Rosenberg, Bethlehem,

N.Y.; James G. Miller, Fort Lauderdale, Fla.

[73] Assignee: Sterling Drug Inc., New York,

[22] Filed: Dec. 7, 1970 [21] Appl. No.: 95,991

[52] US. Cl ..424/273, 424/17 [51] Int. Cl. ..A01n 9/22, A01n 17/08 [58]Field of Search ..424/273, 17; 260/3096 [56] References Cited UNITEDSTATES PATENTS 3,113,071 12/1963 Derse et al ..424/17 Archer ..260/309.6Vassiliates ..424/17 X Primary Examiner-Albert T. Meyers AssistantExaminerbeonard Schenkman Att0rneyElmer .I. Lawson, B. Woodrow Wyatt,Thomas L. Johnson, Robert K. Bair, William G. Webb, Frederik W. Stonner,Roger T. Wolfe and Lynn T. Fletcher [57] ABSTRACT Rodent repellent androdenticidal compositions containing as the active ingredientl-(2-imidazolin-2-ylmethyl)-3-ethylindole and methods of combattingrodents comprising orally administering an effective rodent repellent orrodenticidal quantity of the active ingredient.

14 Claims, No Drawings RODENTICIDAL AND RODENT REPELLENT COMPOSITIONSThis invention relates to the art of combatting rodents, anditparticularly relates to compositions and methods for eitherexterminating rodents or for merely repelling, without killing, rodentsfrom areas or from materials which they would otherwise damage ordestroy in the process of following their normal feeding habits.

The problem of combatting rodent infestation or attack on areas ormaterials vital to mans welfare by use of chemical agents can beapproached in either one of two ways. The usual approach is to attemptto kill off the offending rodent population by making available torodents in areas usually frequented by them a food bait containing arodenticidal agent. Ideally such rodenticides should have such toxicproperties that they provide essentially a one-dose killing action. Butthe rapidity of onset of the toxic action should, on the other hand, besufficiently delayed that the rodents do not die at the bait site andthus discourage further feeding by other members of the rodentpopulation. One of the most widely used rodenticides,3-(a-acetonylbenzyl)-4- hydroxycoumarin (Warfarin), which causes deathby internal hemorrhaging, is ideal from the standpoint of causingdelayed deaths, but since it requires repeated ingestion, it fails tomeet the one-dose criterion of the ideal rodenticide.

Another approach to combatting rodent infestation or attack is to treatan area or a particular material on which rodents normally feed, andwhich it is desired to protect from rodent damage or destruction, with acomposition which the rodents find from experience is unpalatable orotherwise physiologically objectionable. Such compositions act todiscourage further attack without actually killing off the rodentpopulation. This approach to the problem would be used when, say forecological reasons, it might be undesirable (in the course of protectingan area from destruction by rodents) to kill off large parts of naturalpopulations. For example, the problem of the destruction by rodents ofseeds and seedlings used for reforestation is particularly acute, but inthe interest of preserving a natural balance of wildlife, it would beundesirable in protecting such seeds or seedlings to exterminate anentire rodent population by use of a rodenticide. It would thus bepreferable in this instance to treat the seeds or seedlings to beprotected with a composition which would merely discourage consumptionby the rodents without causing large numbers of deaths.

It has now been surprisingly found that l-(2-imidazolin-2-ylmethyl)-3-ethylindole having the forand which isdisclosed and claimed in Archer U.S. Pat. No. 3,404,156 issued Oct. 1,1968, can, depending upon the quantity administered, function either asonedose rodenticide or as a rodent repellent. Use of this compound infood compositions voluntarily ingested by rodents in the course offeeding therefore offers a means of combatting rodents by either killingor repelling them as desired.

Therefore, in its general aspect, the invention relates to a compositionfor combatting rodents consisting essentially of a food materialcontaining as the active ingredient an effective rodent repellent orrodenticidal amount of l-(2-imidazolin-2-ylmethyl)-3-ethylindole. Theinvention also relates to a method of combatting rodents comprisingorally administering to such rodents an effective rodent repellent orrodenticidal amount of the said active ingredient.

In one of its more specific aspects, the invention relates to rodentrepellent food compositions containing an effective rodent repellentquantity of the said l-(2- imidazolin-Z-ylmethyl)-3-ethylindole as theactive ingredient. It is preferred to admix the active ingredient ineffective rodent repellent amount with an inert, powdery carriermaterial to provide a powdery composition which is then dusted or spreadover areas or on materials on which rodents normally feed. For purposesof describing the invention such powdery carriers are considered foodcompositions, although the primary function of the carrier is to providea vehicle for dispersing the active ingredient onto materials which itis desired to protect from further attack and destruction.

Another aspect of the invention relates to a method for providing rodentrepellency which comprises orally administering to the rodents acomposition containing an effective rodent repellent amount of the said1-(2- imidazolin-2-ylmethyl)-3-ethyl-indole as the active ingredient.Administration of the repellent composition is accomplished by treatinga surface or a material on which rodents normally feed with acomposition containing the active ingredient in effective rodentrepellent amount.

In still another aspect, the invention relates to rodenticidalcompositions containing an effective rodenticidal quantity ofl-(2-imidazolin-2-ylmethyl)-3- ethylindole as the active ingredient. Itis preferred to admix the active ingredient in efiective rodenticidalamount with an inert carrier feed material to provide a feed bait forvoluntary ingestion by the rodents.

In still another aspect, the invention relates to a method for killingrodents which comprises orally administering to rodents by the voluntaryfeeding process an effective rodenticidal quantity of the said l-(2-imidazolin-2-ylmethyl)-3-ethyl-indole. The active ingredient ispreferably admixed in effective rodenticidal quantity with a foodmaterial to provide a food bait.

When used as a rodent repellent, the active ingredient is preferablymixed, either in the form of the free base or as an acid-addition salt,with a feed material, for example cereal grain, or with an inert,powdery material (e.g. starch, cornflour, talcum, and the like) toprovide a dry dusting powder for spreading over areas or on materials tobe protected. In such mixtures, the active ingredient preferablycomprises from 0.001 to 0.015 percent by weight of the repellentcomposition. Such repellent compositions are either placed in an areafrom which it is desired to discourage rodents, or

5 alternatively materials to be protected from rodent consumption, suchas seeds or seedlings, are dusted with a powdery repellent compositionas described above. At the above-indicated concentration of the activeingredient, rodents will consume some of the sotreated feed or materialstreated with the dusting composition, but at the levels of activeingredient indicated, few animals will ingest sufficient food materialto absorb a lethal quantity of the active ingredient. Infact theanimals, after ingesting sub-lethal amounts of the treated foodmaterial, consume progressively smaller amounts of such treatedmaterials after several exposures thereto until after a period of aroundtwo to four days, they become hesitant to accept any more of the treatedfood material. A substantial decrease in the rate of attrition ofmaterials to be protected is thus achieved while at the same timeavoiding needless extermination of an entire rodent population. Aparticularly preferred composition for achieving such rodent repellentaction is one in which the active ingredient comprises 0.005 to 0.009percent by weight of the repellent composition.

When used as a rodenticide, the active agent is advantageously mixed,either in the form of the free-base or as an acid-addition salt, with afeed material, for example a cereal grain such as cornmeal, wherein theactive agent comprises from 0.05 to 0.15 percent by weight of the feedmaterial. Obviously higher concentrations of the active agent can beutilized effectively, but no advantage is gained thereby, because due tothe rapidity of onset of toxic symptoms at higher concentrations, thereis some likelihood that the animals would die near the bait site thuscausing unwanted bait shyness in the surviving members of thepopulation. Furthermore, the active ingredient can, if desired, bedisguised in an otherwise highly palatable food bait by incorporatingthe active ingredient therein in an encapsulated, delayed release form.When the rodenticidal agent is ingested in such form, the rodents failto experience the repellent effects of the active ingredient, andtherefore they will generally consume near normal quantities of foodwhile simultaneously ingesting proportionately larger quantities of theactive rodenticidal agent. It is thus possible, by using suchencapsulation methods, to employ a much broader range of concentrationsof the active ingredient, e.g. from 0.003 to 0.45 percent based on thetotal weight of the composition. Preferred rodenticidal compositions areones in which the active ingredient in unencapsulated and encapsulatedforms comprises, respectively, 0.07 to 0.09 percent and 0.005 to 0.010percent by weight of the feed mixture. Such concentrations provide asufficient delay in the time of death following oral ingestion so as toavoid the above-indicated problem arising from too rapid onset of toxicaction while at the same time providing an overall high kill rate.

While the invention herein is specifically exemplified by use of aparticular acid-addition salt of the subject 1-(Z-imidazolin-Z-ylmethyl)-3-ethylindole, either the free base itself orother acid-addition salts are all effective in the practice of theinvention and are considered to be within the purview thereof. In factthe use of water insoluble salts of the said 1-(2-imidazo1in-2-y1-methyl)-3-ethylindole are specifically considered to be useful in thepractice of the invention, because they afford a ready means ofcontrolling the physiological absorbability of the active compound andthus permit further control over the rapidity of onset of toxic effectsof the subject compositions.

The following test procedures were used for determining the rodentrepellent and rodenticidal effects of 1-( 2-imidazolin-2-y1methyl)-3ethylindole.

Test 1. A food bait material was prepared by thoroughly mixing apremixture containing 5 percent by weight of1-(2-imidazolin-2-ylmethyl)-3-ethylindole hydrochloride and cornstarchwith dry cornmeal in an amount to provide a'final concentration in thefood material of 0.008 percent of the active ingredient on aweight/weight basis.

This food material was made available ad libitum over a four day periodto five male rats weighing from 324-376 grams which had been fasted forthe previous twenty-four hours and whose normal food consumption was25-30 grams/day/rat. The amount of treated cereal bait in grams consumedby each of the rats over a period of four days is given in the followingtable.

From the above it will be seen that with repeated exposure to andexperience with the treated cereal grain on a day-to-day basis, the testanimals developed an increasing distaste for the food bait as evidencedby a sharp reduction in their daily food consumption rate, even on thefirst days exposure to the treated food, and by a progressive,day-by-day decrease in the daily consumption of the treated cerealgrain. Even though no food other than that containing the activeingredient was available to the animals during the four day experiment,all animals survived the test despite severe emaciation of all animalsin the group. Moreover, when untreated food was made available to themfollowing the test period, all animals ate voraciously and all returnedto their original weight levels within a few days.

Test II: A cornmeal food bait containing 0.008 percent of the activeingredient on a weight/weight basis was prepared as described above inTest I. This bait was made available to eight male and seven female micead libitum on the third and fourth day following two days of a normaldiet consisting of untreated cornmeal. The total amounts of foodmaterial in grams consumed by the groups of male and female mice on aday-to-day basis are given in the following table.

The above data show that consumption of cornmeal treated with the activeingredient decreased an average of 83-87 percent on the first day andfrom 74-80 percent on the second day of exposure of the mice to thetreated food material over the normal consumption rate. As in Text 1above, no food other than the treated cornmeal bait was available to theanimals during the third and fourth days of the experiment. One animaldied on each of days 3 and 4. The survivors, despite severe emaciation,returned to their normal weights within a few days when a normal dietwas restored to them following the test.

Test III: A cornmeal bait containing 0.08 percent of the activeingredient on a weight/weight basis was prepared as described above inTest I. This bait when offered ad libitum to a group of ten ratsafforded an 80 percent kill rate in a 24 hour period of an averageconsumption of from l-3 grams of treated bait per rat. Deaths in thegroup of test animals began as soon as one hour following ingestion, andtoxic manifestations, consisting of piloerection, face washing, andstretching movements, began occurring about minutes after ingestion.

We claim:

1. A composition for combatting rodents comprising a food material andas the active ingredient an effective rodent repellent or rodenticidalamount of l-(2- imidazolin-Z-ylmethyl)-3-ethylindole.

2. The composition of claim 1 for repelling rodents containing as theactive ingredient an effective rodent repellent amount ofl-(2-imidazolin-2-ylmethyl)-3- ethylindole.

3. The composition of Claim 1 for killing rodents containing as theactive ingredient an effective rodenticidal amount ofl-(2-imidazolin-2-ylmethyl)-3- ethylindole.

4. The composition of Claim 2 comprising, as the food material, a dry,powdery carrier material and wherein the active ingredient comprisesfrom 0.001 to 0.015 percent by weight of the total composition.

5. The composition of Claim 3 wherein the active ingredient comprisesfrom 0.05 to 0.15% by weight of the total composition.

6. The composition of Claim 4 wherein the active ingredient comprises0.005 to 0.009 percent by weight of the total composition.

7. The composition of claim 5 wherein the active ingredient comprises0.07 to 0.09 percent by weight of the total composition.

8. The method for combatting rodents comprising orally administeringthereto an effective amount of the composition of claim 1.

9. The method for repelling rodents comprising orally administering torodents an effective amount of the composition of claim 2. v

10. The method for killing rodents comprising orally administeringthereto an effective amount of the composition of claim 3.

11. The method for repelling rodents comprising orally administering torodents an effective amount of the composition of claim 4.

12. The method for killing rodents comprising orally administeringthereto an effective amount of the composition of claim 5.

13. The method for repelling rodents comprising orally administering torodents an effective amount of the com position of lairn 6.

14. T e method or killing rodents comprlslng orally administeringthereto an effective amount of the composition of claim 7.

2. The composition of claim 1 for repelling rodents containing as theactive ingredient an effective rodent repellent amount of1-(2-imidazolin-2-ylmethyl)-3-ethylindole.
 3. The composition Of Claim 1for killing rodents containing as the active ingredient an effectiverodenticidal amount of 1-(2-imidazolin-2-ylmethyl)-3-ethylindole.
 4. Thecomposition of Claim 2 comprising, as the food material, a dry, powderycarrier material and wherein the active ingredient comprises from 0.001to 0.015 percent by weight of the total composition.
 5. The compositionof Claim 3 wherein the active ingredient comprises from 0.05 to 0.15% byweight of the total composition.
 6. The composition of Claim 4 whereinthe active ingredient comprises 0.005 to 0.009 percent by weight of thetotal composition.
 7. The composition of claim 5 wherein the activeingredient comprises 0.07 to 0.09 percent by weight of the totalcomposition.
 8. The method for combatting rodents comprising orallyadministering thereto an effective amount of the composition of claim 1.9. The method for repelling rodents comprising orally administering torodents an effective amount of the composition of claim
 2. 10. Themethod for killing rodents comprising orally administering thereto aneffective amount of the composition of claim
 3. 11. The method forrepelling rodents comprising orally administering to rodents aneffective amount of the composition of claim
 4. 12. The method forkilling rodents comprising orally administering thereto an effectiveamount of the composition of claim
 5. 13. The method for repellingrodents comprising orally administering to rodents an effective amountof the composition of claim
 6. 14. The method for killing rodentscomprising orally administering thereto an effective amount of thecomposition of claim 7.